As they bowled out the Foxes for 483 at Hove by 15 runs, Unadkat took 6-94 from 32.4 overs, including the last four wickets in 31 balls.

A trip to Derbyshire next week precedes a home game against Gloucestershire, but second-placed Worcestershire, who currently have an 18-point advantage over Sussex, remain favourites for promotion. Next week, they will play Durham at New Road before finishing at Headingley.

While Leicestershire, with Colin Ackermann’s 136, Umar Amin’s 94 and Tom Scriven’s 78, remain in contention for Division One next year, they face Yorkshire at home before finishing at the top.

As Ackermann and Amin put on 180 for the fourth wicket, Scriven and Ben Cox added 120 for the seventh to take Leicestershire within 46 runs of victory.

Both established batters were defeated by some bounce and seam movement on a benign surface. After making a career-best score, Scriven edged half-forward and was taken at head height at slip by Tom Alsop before Scott Currie nibbled at a full-length delivery for a second-ball duck.

It left Chris Wright, who will join Sussex next season, and last man Matt Salisbury needing 43, with Salisbury batting with a runner due to a hamstring injury.

When Wright slapped Fynn Hudson-Prentice for two sixes to help get the target down to 16, Sussex nerves were jangling again after he had led Leicestershire to a target of 389 against Yorkshire earlier this season. However, Unadkat produced an outstanding leg-stump yorker that beat Wright to the tee.